The conversion of gas oils and higher boiling portions of crude oils referred to as residual, reduced crudes or resids by thermal and catalytic processes employing fluidizable solid particle material has been discussed in numerous published articles and is the subject of considerable prior patent art. Some petroleum refiners consider some heavy oil cracking operations to be a practical and profitable operation. However, it is generally agreed that as you increase the end boiling point of the heavy oil feed so also does it aggrevate the fluid contact operation by the accumulation of metal contaminants and carbon producing components such as asphaltene type material contributing to Conradson carbon when the feed end point is increase beyond about 538.degree. C. or 552.degree. C. (1000.degree. F. or 1025.degree. F.).
Fluid cracking units and particularly fluid catalytic cracking technology has improved dramatically over the past twenty years as well as the apparatus in which accomplished particularly with the development of high activity crystalline zeolite cracking catalyst considered more heat stable than the amorphous cracking catalyst earlier employed permitted increasing the severity of the cracking operation to a level restricted substantially by the heat available in a given refinery operation. The heat available in any given operation is dependent upon the carbon burning capacity of the system and the metallurgical limits imposed on the catalyst regeneration (combustion) section of the refinery cracking system. Providing additional available heat by combustion of some Conradson carbon carbonaceous deposits will usually permit expansion of its cracking capacity. This method has been employed by many refiners since the zeolite catalysts tend to produce less coke and high boiling recycle material whereby the feed end point and throughput to the cracking unit may be increased. A further significant improvement contributing to increased feed throughput and thus yields has been the result of improved catalyst regeneration techniques. High regeneration temperatures tend to permit one to lower the residual carbon level on the regenerated catalyst particles and this lowers the catalyst to oil ratio employed in the hydrocarbon conversion zone. The catalyst regeneration operations have been improved to include complete CO combustion in the presence of heat absorbing catalyst particles whereby the undesired condition of after burning can be eliminated.
However, as these advancements were made so also were there some disadvantages experienced by the higher regeneration temperatures when exceeding about 704.degree. C. or 760.degree. C. (1300.degree. F. or 1400.degree. F.). That is, the apparatus encountering the high temperature regeneration operation, such as flue gas ducting valves, VGO boilers, etc. all required metallurgical upgrading in combination with being provided with refractory lining materials suitable for the temperatures encountered. Thus, the combinations of improved alloys and carbon steel suitably refractory lined has permitted prior art regeneration technology to contemplate and encounter temperatures within the range of 704.degree. C. to 871.degree. C. (1300.degree. F. to 1600.degree. F.) but more usually not above about 815.degree. C. (1500.degree. F.). In fact, it is generally preferred to restrict regeneration temperatures not to exceed about 732.degree. C. (1350.degree. F.) to preserve catalyst activity. It was also learned that the catalyst had to remain in a regenerator long enough to allow desired carbon burn off and the carbon burning rate was influenced by the combination of oxygen partial pressure therein and the temperature available to achieve rapid ignition of carbonaceous material on charged spent catalyst. The higher temperature catalyst regeneration operation imposed further hardships on the particles of catalyst contributing to the production of considerable catalyst fines exiting with the flue gas products of combustion. Such flue gas containing particle fines have caused considerably undesired impact upon the surrounding environment. Furthermore, the flue gases contain particulates which are both condensible and solid particulate matter of considerable cracking activity. The loss of such active cracking catalyst fines requires replacement and reduces the economic value of the cracking process.
The present invention is concerned with the method and means for regenerating fluidizable solid particle material whether inert or catalyst particles whereby the removal of deposited carbonaceous material from the particles is achieved to a desired low level and the recovery of heated catalyst particles including formed catalyst fines are recovered at a sufficiently high order of magnitude to meet very strict opacity standards and solids loss criteria effecting the cracking process economics.